As is known, double-cylinder circular machines for knitting hosiery items or tubular articles in general comprise a supporting structure which is composed substantially of a footing which rests on the ground and supports the lower needle cylinder so that it can rotate about its own axis, which is oriented vertically.
The footing also supports, by means of a column that rises vertically from the footing, the upper needle cylinder, which is arranged above and coaxially with respect to the lower needle cylinder.
The actuation cams of the sliders or transfer sinkers are arranged around the lower needle cylinder and around the upper needle cylinder and are accommodated inside axial slots defined on the lateral surface of the needle cylinders. The sliders are adapted to engage respectively the lower or upper tip or head of the needles of such machines, which are typically provided with a tip or head at both of their ends. The sliders are provided with heels, which protrude from the lateral surface of the needle cylinder in which they are accommodated and can be engaged, as a consequence of the rotation of the needle cylinders about their own axis relative to the actuation cams, with paths defined by the actuation cams. Such paths are shaped so as to cause the movement of the sliders with respect to the needle cylinders parallel to the axis of the needle cylinders. This movement of the sliders is used to actuate the needles, for example to move the needles to knit at a feed or drop of the machine, or to transfer the needles from the lower needle cylinder to the upper needle cylinder or vice versa.
The lower needle cylinder can be actuated with a rotary motion about its own axis by means of an electric motor, which is accommodated inside the footing and is connected, by means of its shaft, to the lower needle cylinder by way of a gear-type or toothed-belt transmission. The same electric motor is connected to the upper needle cylinder so as to actuate the upper needle cylinder with a rotary motion about its own axis, synchronously with the rotation of the lower needle cylinder. More particularly, the shaft of the electric motor accommodated in the footing is connected, by way of a gear-type or toothed-belt transmission, to a transmission shaft, which is supported, so that it can rotate about its own vertically oriented axis, inside the column that supports the upper needle cylinder. This transmission shaft is connected, proximate to its upper end, to the upper needle cylinder by way of a gear-type or toothed-belt transmission.
The arrangement of the electric motor that actuates the needle cylinders inside the footing can hinder and make it difficult to place, in this portion of the machine, other components required for its operation, such as for example the electrical cables that connect the several components of the machine to the electrical panel, which is usually applied to a door located on a lateral face of the footing.
Moreover, the arrangement of the electric motor in the footing can make it difficult to install devices for tensioning the articles being knitted, which descend into the lower needle cylinder and exit from its lower end.